Carsten Ziegeler created SLING-2896: ---------------------------------------
Summary: Job might be executed twice if a topology event occurs Key: SLING-2896 URL: https://issues.apache.org/jira/browse/SLING-2896 Project: Sling Issue Type: Bug Components: Extensions Affects Versions: Extensions Event 3.2.0 Reporter: Carsten Ziegeler Assignee: Carsten Ziegeler Fix For: Extensions Event 3.2.0 If a parallel queue is used (either parallel or round robing) with a limit of N parallel jobs and there are X > N jobs in the queue, the (N+1) job might get processed twice if a topology change occurs: Assume we have a parallel queue with max parallel processing set to 8 and 15 jobs entering the queue. The AbstractParallelJobQueue.start is called with the first 8 jobs - all fine, limit is not yet hit, those jobs are started When AbstractParallelJobQueue.start is called with job #9 the acquireSlot() method waits, since the queue is full/busy: The waiting is done in acquireSlot(), in the syncLock.wait() (line 78 of AbstractParallelJobQueue). The calling method - start(JobHandler) - keeps a reference to job #9 ! In the meantime a TopologyEvent occurs. AFAICS this triggers 'outdating' the existing and recreating a new queue. The BackgroundLoader.loadJobsInTheBackground starts filling the new queue. Unfortunatelly, this Backgroundloader schedules job #9 too - since it is not yet marked in the repository in any way (there's only the previous queue which has a reference to it in above mentioned start(JobHandler) method - but the job #9 is not yet marked as running in the repository). => Thus job #9 is executed the first time by the new queue. Eventually the outdated queue is finished with execution. The above acquireSlot() method returns, and: => job #9 is executed the second time (by the outdated queue). -- This message is automatically generated by JIRA. If you think it was sent incorrectly, please contact your JIRA administrators For more information on JIRA, see: http://www.atlassian.com/software/jira